The present invention is directed to an electric drive for paper processing machines having at least two rotary subassemblies.
From the German Patent Application No. 199 30 998 A1, a printing press drive is known which is designed as an external-rotor motor. Its rotor is equipped with permanent magnets and is assigned to at least one cylinder of the printing press as its drive, with the stator being in a fixed connection with the side frame of the printing press. In addition, on its exterior, the rotor has a ring gear by way of which it contacts other gear wheels of a gear train of the printing press. In this manner, at least one cylinder of the printing press is directly driven and is, nevertheless, in contact via one gear train with other cylinders of the printing press and their drive. In this manner, as well, the cylinder and its drive are synchronized with other drives and cylinders of the printing press. To connect the rotor to the gear train, the ring gear can be rotationally mounted on the rotor. This enables the ring gear to be rotated with respect to the rotor to enable angular adjustments of the cylinder to be made with respect to the gear train.
In addition, from European Patent No. 0 812 683 B1, a drive for a sheet-fed offset press is known. In this case, the cylinders or drums or one or more print units are interconnected via a gear train and driven by at least one drive acting on this gear train. Moreover, in each print unit, there is at least one plate cylinder or blanket cylinder which is mechanically decoupled from the gear train and is driven by an assigned drive, as the case may be, in a specifiable manner. Thus, in the context of such a sheet-fed offset press, some drums and cylinders are constantly driven by a gear train, while other cylinders are driven by a separate drive. As a general principle, the latter components are not connected to the continuous gear train.
The drawback of the approach according to German Patent Application 199 30 998 A1 is that the cylinders of a printing press are in continuous contact with the gear train of the printing press, so that it is not possible to vary the rotational speed or the direction of rotation of the individual cylinders. It may be that the other approach known from European Patent No. 0 812 683 B1 does allow a cylinder-specific drive, but its disadvantage is that the individually driven cylinders are not connected to a gear train. This, in any case, necessitates a costly electronic synchronization of the cylinders.
It is also known to connect cylinders on one side to a gear train and, on the other side, to a direct drive. In such a case, the cylinders are connected via a coupling to the gear train. The significant disadvantage here, however, is that a mechanical or electromagnetic coupling must be provided, which takes up space and entails costs.